$\dfrac{2}{5} + \dfrac{5}{8} = {?}$
Explanation: ${\dfrac{2}{5}}$ ${\dfrac{5}{8}}$ $+$ ${\dfrac{2 \times 8}{5 \times 8}}$ ${\dfrac{5 \times 5}{8 \times 5}}$ $+$ ${\dfrac{16}{40}}$ ${\dfrac{25}{40}}$ $+$ $ = \dfrac{{16} + {25}}{40} $ $ = \dfrac{41}{40}$